Oil in Liquid sight glass

I am seeing a large amount of oil accumalate in the liquid sight glass on a system and a loss of oil in the compressor .
But I thought the oil would sit in the evaporator during oil loss problems ?

Any advice much appreciated

Thanks

Could you describe the system? How many compressors, evaporators does it have a discharge oil separator, liquid reciver, suction separator... Tnx

Short of refrigerant?

Oil is normally carried around the system with the refrigerant but when there is a shortage of refrigerant the oil will accumulate wherever the refrigerant flow is low. (I assume the sight glass got a larger diameter than the liquid line?)

:cool:

Liquid floodback. Cold compressor. oil foaming.

If it is a system that was retrofitted it could be the mineral oil that is floating around the system ,depending on the angle of the sight glass ie horizontal it can sit on the top of it for a while and would be very noticeable as it doesnt mix too well but will still travel around a ht system fairly easily.

Fluid chiller , single recip comp , no liquid receiver , no oil sep , no accumulater , close coupled
The sight glass is the very deep type, that always seems to have to fill up .

Strange thing is that the sight glass will be full to start ( at higher water temp) then slow fill with oil and noticeable drop oil loss in comp , not much cooling happening , but superheat is Low , the after a while sight glass will start flashing (seem to partly empty) and no sign of oil, and oil level in comp will return.
But I do think there maybe a little flooding back as oil temp does drop .

It has been retrofitted in past to 407a , but has had numerous oil changes , I guess it could be some mineral oil , but still seem to be losing a large amount of oil from compressor

From what you are describing the oil fluctuations/migration is a symptom and not a cause.

Check your refrigerant level and meetering device(s).

:cool:

Got crankcase heaters?... pumpdown?... elevated evaporator?... overcharged?

I had same problem 4 years ago and i find filter dryer is half blocked I changed that every thing went well.
so check your filter .